1. Field of the Disclosure
The disclosure relates to compositions of manganese sulfide (MnS) compounds useful as additives for making a sintered product to enhance machinability and, more particularly, to compositions of a MnS compound useful as additives for making a sintered product that can be preserved for a long time by enhancing resistance to moisture in the air.
2. Discussion of the Related Art
Generally, manganese sulfide (MnS) is a kind of a metal sulfide and is used as an additive to raw materials to enhance machinability in making a sintered product. The MnS may be used as a solid lubricant.
Currently manufactured MnS is a pure form of MnS, which is manufactured so that sulfur (S) rather than manganese (Mn) is in excess. Surplus sulfur reacts with oxygen, zinc, and the like under the atmosphere of a sintering furnace during the sintering process, resulting in problems. For example, excess sulfur erodes mesh belts of heat-resistant steel, muffle, or fireproof material, which is formed in the furnace, and may remain on a surface of the product to cause sooting.
To solve such problems, to make up for heat loss in the manufacturing process, and to improve productivity, a manganese sulfide compound and its method of production have been disclosed in U.S. Pat. No. 5,768,678. In this patent, a MnS compound of Fe—Mn is manufactured. In this case, since a considerable amount of sulfur remains in excess, the problems described herein still occur in the sintering process.
Recently, attempts to manufacture a metal sulfide by mixing sulfur with metal using a mechanical-chemical method have been made in Korean Patent Applications Nos. 1999-0026303, 2001-0007298, and 2001-0007299. In case of MnS manufactured by this method, excess sulfur has been considerably reduced. However, a problem still remains in the sintering process. Also, since such MnS has hygroscopic that absorbs moisture in the air, problems occur in preservation and use after manufacturing it.